JP5399646B2 - Neutral paper making method - Google Patents

Description

  The present invention relates to a neutral papermaking method that uses calcium carbonate as a filler and suppresses dissolution of calcium carbonate that occurs during the papermaking process.

  In general, paper used for printing or writing is usually required to have whiteness, opacity, smooth printing suitability, writing suitability, etc., but the pulp cannot be used alone to satisfy the required properties, so the filler is made. It is often overwhelmed. As a papermaking method in which the filler is incorporated, an acidic papermaking method using talc, titanium dioxide or the like at a pH of around 4.5, or a calcium carbonate (light, heavy) from weakly acidic to weakly alkaline at pH 6 to 8.5. There is a neutral papermaking method that uses the quality. In particular, in recent years, there is a high demand for neutral paper from the standpoints of paper storage stability, paper quality, environment, and the like, and it is becoming popular. In this neutral papermaking method, calcium carbonate is a filler that is preferably used in terms of physicochemical properties, quality, cost, and the like. However, since calcium carbonate dissolves slightly even in the vicinity of neutrality, even in the neutral papermaking process, it partially dissolves from the time of pulp slurry preparation to the time of papermaking. It is necessary to add.

  In recent years, in the papermaking process, in order to reduce the amount of water discharged out of the system from the viewpoint of saving water, the so-called papermaking process has been closed to increase the circulating water in the process and keep the use of new new water low. Yes. Calcium carbonate dissolved in the pulp slurry by the neutral papermaking method will increase the calcium ions in the dehydrated filtrate (white water) after paper making, and this will add to the situation of white water closing, resulting in high calcium ions and carbonate ions. Concentrate. This is the biggest factor of calcium scale in the process that plagues the paper mill.

In the papermaking process in which calcium carbonate is contained in the pulp suspension, as a method for suppressing dissolution of calcium carbonate in the papermaking system, carbon dioxide is added at a pH of 8 or less in the pulp slurry to which calcium carbonate is added. A method to be introduced (Patent Document 1) has been proposed. According to this method, the amount of free calcium ions in the pulp slurry and circulating process water can be reduced, and accumulation of calcium ions is prevented.
In addition, an invention has been proposed in which calcium carbonate is used as acid-resistant calcium carbonate that can be used as a filler for producing neutral or weakly acidic paper (Patent Document 2).

However, there is no proposal regarding an effective dissolution inhibitor of calcium carbonate that can suppress the dissolution of the calcium carbonate pigment only by adding a predetermined amount into the pulp slurry and does not become a source of white water contamination.
Japanese translation of PCT publication No. 2002-509992 Special Table 2000-506486

  In view of such circumstances, the present invention provides a neutral papermaking method that can reduce the amount of calcium carbonate added and suppress calcium scale during the process by improving the dissolution of calcium carbonate in neutral papermaking. There is.

  In order to solve the above problems, the present invention has the following configuration.

(1) A neutral papermaking method using calcium carbonate as a filler, wherein phosphorylated starch having a bound phosphorus content of 0.2% by mass or more is added during pulp slurry preparation.

(2) The neutral papermaking method according to (1), wherein phosphorylated starch is added to the pulp slurry before adjusting the pH of the pulp slurry.

(3) The neutral papermaking method according to (1) or (2), wherein the pH of the prepared pulp slurry is 5.5 to 8.5.

  According to the present invention, the amount of calcium carbonate added can be reduced by improving the dissolution of calcium carbonate in neutral papermaking, and the calcium scale in the process can be suppressed by reducing the dissolved calcium carbonate flowing into the white water. It becomes possible.

Hereinafter, the present invention will be described in detail.
The neutral papermaking method in the present invention can achieve the object by adding and mixing phosphorylated starch to the pulp slurry before pH adjustment or immediately after pH adjustment at the time of pulp slurry preparation before papermaking.

  The phosphorylated starch used in the present invention includes starch to which a phosphate ester group is added, and dextrins, oligosaccharides, monosaccharides, etc., which are degradation products of starch, and those having a phosphate ester group bonded thereto. Saccharides other than glucose such as hexoses such as fructose, mannose and galactose, and pentoses such as xylose, arabinose and ribose, and cellobiose having glucose as a constituent saccharide but different binding states , Oligosaccharides such as laminaribiose and gentiobiose, and polysaccharides such as dextran and cellulose, each having a phosphate group bonded thereto. In addition, as long as the phosphate ester group is bonded, other physicochemical treatments such as oxidation, cationization, acetylation, carboxymethylation, crosslinking, urethanization, alphalation, reduction, etc. It may be. As starch, starch of cereals such as corn starch, wheat starch and rice starch, and starches of roots such as potato starch and tapioca starch are used.

  The method for preparing phosphorylated starch can be arbitrarily selected from known methods. In general, a phosphate is mixed with starch or saccharide, followed by a dry heating reaction. Moreover, the method of phosphorylating using enzymes, such as a phosphatase and a phosphorylase, is also employable.

  The phosphorylated starch used in the present invention needs to contain 0.2% by mass or more of bound phosphorus, and more preferably 0.4% by mass or more. In order to develop the effect of the method of the present invention, the phosphorylated starch must be dissolved in the pulp slurry. Therefore, in the case of insoluble in cold water, it is necessary to dissolve by heating in water in advance or by adding alkali or the like before addition. What is soluble in cold water may be added to the pulp slurry as a powder, or may be added after previously dissolving in cold water. The concentration of phosphorylated starch when it is dissolved in water and then added to the pulp slurry can be arbitrarily set as long as a solution having a viscosity that is sufficiently dissolved and does not hinder the work can be prepared. It is in the range of 1% by mass to 70% by mass.

  The place where phosphorylated starch is added to the pulp slurry may be any place as long as it is before papermaking, but after a long time has elapsed since the addition of calcium carbonate (light, heavy), Therefore, it is more effective to add phosphorylated starch before or immediately after the addition of calcium carbonate. It is also possible to pre-mix phosphorylated starch with calcium carbonate slurry before addition to the pulp slurry, and to mix with other chemicals if the phosphorylated starch can maintain its performance without causing aggregation. You can also keep it.

  If the amount of phosphorylated starch added is 0.01 parts by mass or more with respect to 100 parts by mass of calcium carbonate, the effect is exhibited, and the effect is improved as the amount added is increased. However, even if it is added at a ratio of 100 parts by mass or more, it is not possible to expect an effect more than that corresponding to the increase of the addition amount. Practically, 0.1 to 10 parts by mass is preferable.

Pulp used for the neutral papermaking method in the present invention is not particularly limited, and commonly used known papermaking pulp can be applied, chemical pulp such as sulfite pulp, kraft pulp, soda pulp, semi-chemical pulp, Any of wood pulp such as mechanical pulp, non-wood pulp, and deinked pulp obtained by treating waste paper may be used, and unbleached pulp and bleached pulp may be used.
The pH at the time of papermaking is generally effective at pH 5.5 to 8.5 where neutral papermaking is performed. Papermaking paper strength enhancer, wet paper strength enhancer, filler other than calcium carbonate, sizing agent, step Known paper making chemicals such as a retention improver, a dye, an antifoaming agent, an antiseptic, and the like can be added as necessary, and there is no limitation on the type, amount added, and order of addition. A known high yield system can also be used in combination.

  Hereinafter, the present invention will be described more specifically with reference to evaluation tests and examples, but the present invention is not limited to these examples. Moreover, the following% and part are the mass% and the mass part unless otherwise specified.

[Production of phosphorylated starch]
1200 kg of corn starch (manufactured by Oji Cornstarch Co., Ltd., 13% moisture) is introduced into the turbulator (mixer) at a constant flow rate, and at the same time, 176 kg of primary sodium phosphate dihydrate and 32 kg of anhydrous dibasic sodium phosphate are dissolved in water. A total amount of 655 kg of phosphate solution was added at a constant flow rate and mixed uniformly. This phosphate mixed starch was dried with a flash dryer until the water content reached 6%. 500 kg of the obtained phosphate-impregnated starch (phosphorus content 3.5%) was put into a fluidized bed heating machine, heated hot air was supplied and fluidized, and heated at 175 ° C. for 120 minutes. The recovered phosphorylated starch (bound phosphorus content 2.8%) was 450 kg.
The phosphorylated starch obtained by the above method is soluble in cold water that dissolves only by being dispersed in cold water (20 ° C.), and was used as a sample for the following evaluation tests and examples.

<Evaluation test>
Phosphorylated starch solution prepared by dissolving 100 ml of 0.5% LBKP (hardwood bleached kraft pulp) slurry at a concentration of 1% with stirring was 100 parts of calcium carbonate, and the amount of phosphorylated starch (absolutely dry) was 0 part (blank). 1 part, 1 part, 10 parts were added in a ratio of 30 parts, and after stirring for 30 seconds, 2 ml of 10% W / V light calcium carbonate (trade name: Tama Pearl TP-121, manufactured by Okutama Kogyo) was added, and 30 After a second, the pH was adjusted to 7.5 or 6.5 with a small amount of dilute sulfuric acid. The pH is maintained for 30 minutes, immediately after pH adjustment, and after 5 minutes and 30 minutes, 1 ml of pulp slurry is collected and immediately filtered through a membrane filter having a pore diameter of 0.2 μm, and the Ca concentration of the filtrate is adjusted to Ca. The amount of calcium carbonate dissolved was determined by measuring with a measurement kit (trade name: Calcium C Test Wako, manufactured by Wako Pure Chemical Industries) and converting to calcium carbonate. The calcium carbonate dissolution inhibition rate was determined from the following formula.
Calcium carbonate dissolution inhibition rate (%) = [1- (calcium carbonate dissolution amount when phosphorylated starch is added / calcium carbonate dissolution amount when phosphorylated starch is not added (blank))] × 100
The results are shown in Table 1.

  As is apparent from Table 1, it can be confirmed that the dissolution of calcium carbonate is largely suppressed by adding phosphorylated starch at both pH 7.5 and 6.5.

<Example 1>
Canada Standard Freeness (CSF) 450ml LBKP (hardwood bleached kraft pulp) slurry (pulp concentration 1%) 100ml of 1% phosphoric acid starch solution as a solid content while stirring 100ml 0.01 parts (trade name: Hymo Lock NR11L, made by Hymo) 0.01 parts (100 parts dry pulp), AKD sizing agent (trade name: size pine) K-910: manufactured by Arakawa Chemical Co., Ltd.) 0.05 parts (100 parts against dry pulp), light calcium carbonate (trade name: Tama Pearl TP-121, manufactured by Okutama Kogyo Co.) slurry as solids, 20 parts (on dry) 100 parts of pulp) was added in this order at 15 second intervals. Further, 0.5 part of aluminum sulfate (100 parts against dry pulp) was added, and the pH was adjusted to 7.0 with dilute sulfuric acid. Stirring was continued for 10 minutes, immediately after pH adjustment, for 0 minutes, and then the whole amount was put into a round handmade sheet machine to prepare a wet paper and dried with a drum dryer. The ash content (calcium carbonate content) of this stock was determined in accordance with JIS P8251.2002.

<Example 2>
The paper was operated in the same manner as in Example 1 except that the addition amount of the 1% phosphorylated starch solution was changed to a ratio of 1 part to 10 parts with respect to 100 parts of the absolute dryness of calcium carbonate to be added later as a solid content. The ash content of the ingredients was determined.

<Example 3>
The same operation as in Example 1 was conducted except that the amount of the 1% phosphorylated starch solution was changed to a ratio of 1 part to 0.1 part with respect to 100 parts of the absolutely dry calcium carbonate to be added later as the solid content. The ash content of the paper was calculated.

<Example 4>
The ash content of the stock was obtained in the same manner as in Example 1 except that the amount of bound phosphorus in the phosphorylated starch was changed from 2.7% to 0.5%.

<Example 5>
The ash content of the paper stock is the same as in Example 1 except that acetylated phosphorylated starch (2.5% bound phosphorus) having an acetyl group of 0.02 substituted is used instead of phosphorylated starch. Asked.

<Comparative Example 1>
The ash content of the paper stock was determined in the same manner as in Example 1 except that phosphorylated starch was not added.

<Comparative example 2>
As an example of starch other than phosphorylated starch, the same procedure as in Example 1 was performed except that oxidized starch (trade name: Ace A, manufactured by Oji Corn Starch Co., Ltd.) having an oxidation degree of 3.2% was used. Asked.

<Example 6>
The ash content of the paper stock was determined in the same manner as in Example 1 except that the pH was changed from 7.0 to pH 8.0.

<Comparative Example 3>
The ash content of the paper stock was determined in the same manner as in Example 6 except that phosphorylated starch was not added.

<Example 7>
The ash content of the paper stock was determined in the same manner as in Example 1 except that the pH was changed from 7.0 to pH 6.0.

<Comparative Example 4>
The ash content of the stock was determined in the same manner as in Example 7 except that phosphorylated starch was not added.

  As is apparent from Table 2, a paper stock having a high ash content was obtained by the neutral papermaking method of the present invention. Moreover, the effect was acquired also with the phosphorylated starch which combined other functional groups. This result indicates that the ash content of the paper stock is increased by suppressing the dissolution of calcium carbonate by the addition of phosphorylated starch. That is, by using the neutral papermaking method of the present invention, it is possible to obtain the same ash content as that of the blank (Comparative Example 1) even if the calcium carbonate added to the pulp slurry is reduced. Further, by suppressing the dissolution of calcium carbonate, the amount of calcium ions released into the dehydrated filtrate (white water) after papermaking is reduced, leading to suppression of calcium scale.

Claims (2)

When pulp slurry tone formation in neutral papermaking method of using calcium carbonate as a filler, the addition of starch consisting of only bound phosphorus 0.2 mass% or more phosphorylated starch in front of箇plants adding calcium carbonate to the pulp slurry A neutral papermaking method. The neutral papermaking method according to claim 1, wherein the pH of the prepared pulp slurry is 5.5 to 8.5 .